have you tryed the G for ghost, now the ghost should show,
and if you play against a replay you should get the times in top left corner.
O is for opponents but that is for online i guess
you must finish a track to see your best time when playing a downloaded track at the top when your replay is rolling. so just finish and you should see it and if its during validation u just press the flag to see your at and remember you must have the same name on track when you validate or it dissapears. and if you have an old grafic card you cant use to high shader version becouse that is also make your ghost dissapears.